Direction finder antenna system



Aug. 5, 1941.

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ATTORNEY.

1941- E. J. H EFELE I 2,251,708

DIRECTION FINDER ANTENNA SYSTEM Filed April 27, 1937 4 Sheets-.-Sheet 4RADIO RECEIVEP O I .107 65 113 4 J i v 0 1; 0"" 'T RZ Z E ER 'NPUT 711112 i I "I 6 109 L 'R l n m 1- 1 3 AUDIO FREQUENCY 5i OSCILLATOR INV ENTOR. durarwl3.9(e'fele ATTORNEY.

Patented Aug. 5, i941 {UNITE s'm'res PATENT, OFFlQE.

2,251,708 DIRECTION FINDER ANTENNA SYSTEM Edward J. Hefcle, Amityville,N. Y. Application April 27, 1937, Serial No. 139,143

16 Claims.

This invention relates to direction flnders and more particularlyrelates to antenna systems for right-left indicating direction findersystems.

Automatic right-left indicator systems, particularly for aircraft, haveheretofore generally depended upon the formation of cardioid receptionpatterns and used a loop antenna combined with a vertical ornon-directional antenna in a predetermined relation. The resultantcardloid patterns depended upon critical tuning andelectrical phasing ofthe loop antenna system.

Changes in temperature of the loop antenna and slight variations intuning caused serious misphasing at the antenna stage of the radioreceiver and resulted in reception patterns producing null or zerointensity on bearings actually many degrees off-course. Such directionalerrors are very serious, particularly on aircraft where radiodirectional guidance is often. the sole navigational aid.

In accordance with my present invention, I contemplate producingcardloid reception patterns by means of vertical antenna arrays combinedat the antenna input stage in a predetermined manner. The cardioidpatterns of my invention are not dependent upon tuning or criticalvariable electrical conditions but remain constant after installationfor all reception pur- I utilize the vertical antenna array to receptionpatterns for controlling-the deflections of a. right and left indicator.

Vertical mast antenna, even when streamlined, produces an aerodynamicresistance or drag to flight of approximately six pounds at a flightspeed of 200 miles per hour. Accordingly, it is greatly advantageous tominimize the number of mast antennae arrays necessary for accuratedirectional guidance. invention, two, three or four vertical antennaemay be used for such a right-left indicator.

An aircraft traveling at high speed through the atmosphere often passesthrough rain, dust, snow and fog, the particles of which impinge at highvelocityupon the antenna structure and set up .static impulses which aretransmittedv through. to the radio receiver. Such static often seriouslyimpairs reception. Loop antennae have been successfully shielded byenclosing them in a. metallic housing, which housing is placed atgrounded potential at its nodal point. In accordance with my invention,I provide a. metallic shield surrounding the mast antenna and connectthe shield to ground potential through a radio frequency choke coil. Inthis manner, the

In accordance with myenclosed mast antenna.

charges produced by the impinging high velocity particles are dissipatedby conduction to ground through the high impedance choke coil and theradio signals areonly somewhat reduced in intensity as they pass throughthe shield to the By maintaining the shield at a high radio frequencyimpedance, the sensitivity of reception by my novel shielded mastantenna is substantially maintained. preferred construction for ananti-static antenna is the use of a doublet or opposed mast antennaarray, each mast being surrounded by a spaced shield connected to groundby an individual choke coil. All electrical impulses and transients areconducted to ground free of any part of the radio circuit.

Accordingly, it is an object of my present invention to provide a novelmethod of and means .for producing directional reception patterns withindependent of tuning or electrically varying conditions.

A further object of my present invention is to provide a novelanti-static vertical antenna system.

These and other objects of my present invention will become apparent inthe following description of the invention taken in connection with thedrawings, in which:

Figures 1 and 1A are schematic showings of preferred non-directionalantennae enclosed by streamlined shields for eliminating staticelectrical pulses encountered in high speed flight.

Figure 2 is an enlarged cross-sectional view taken along 2 through theanti static mast antenna of Figure 1.

Figure 3 is a fragmentary elevational view of a modified shield for theanti-static mast antenna of my present invention.

Figure 4 is across-sectional view taken along 4-4 of Figure 3.

Figure 5 is a schematic electrical diagram of a right-left indicatoroperating with a double' sponding to Figure 5 and employing balanceddoublet antenna arrays.

Figure 17 is a polar diagram of the right and left cardioid receptionpatterns produced by the antenna system of Fig. 16. v

Figures 18 to 22 illustrate different forms of radio 'c uency time-delaynetworks which may be employed in carrying out certain modifications ofmy present invention.

Figures 23 is a schematic diagram corresponding to Figures 5 and 16showing a preferred timedelay network in circuit with the antennasystem.

Figure 24 is a schematic electrical diagram of a cardioid patternright-left indicator in accordance with my present invention employingical antenna arrays using mechanical e 25 is a schematic electricaldiagram of pattern rightleft indicator in acith my present inventionemploying tical antenna arrays using mechanical Figure 26 is a schematicelectrical diagram of a right-left indicator corresponding to Figure 25but employing electronic switching means at the antenna input andindicator.

In Figure 1 I have shown in elevation a preferred arrangement forshielding the vertical antenna from the effects of static produced byhigh velocity particles encountered in high speed night through fog,dust and storms. The vertical or mast antenna array 30 is supported uponthe exterior surface 3! of a vehicle such as a ship, car or aircraft.Figure 2' is a cross-section taken along 2--2 of Figure 1 and drawn to alarger scale. anti-static shielding as applied to a vertical mastantenna, it is to be understood that it may similarly be applied to thetop and bottom rods of a doublet antenna array as well as to an antennawire supported in any other angular relation with respectto the surfaceof the vehicle.

Although I prefer to illustrate the In my co-pending application SerialNo. 139,142

filed April 27, 1937, I illustrate atrailing wire antenna of an aircraftstatically shielded by the principle herein described for the verticalmast.

The vertical antenna array .30 comprises a central conductor rod 32which is the antenna wire for the radio receiver. Surrounding theantenna wire 32 is a metallic shield 33 preferably shaped in a tear-dropor stream line form having a minimum aerodynamic resistance in thedirection of flight of the aircraft. Accordingly, the leading edge 34ofthe shield 33 is wide and rounded and the trailingedge 35 is narrowand pointed. I prefer to incorporate a solid insulation material 36between the conductor 34 and the metallic shield33 and employ theinsulation 36 to rigidly support the relatively thin and weak shielding33 about the mast structure 30. p I prefer to use a rubber compositionwhichiis moldable and accordingly will grip the corrugations 31 formedon the inner surface of the metal shield 33 to hold the latter in place.Gas-expanded rubber which is of light weight and composedthe vehiclestructure 3|. The bottom edge 33' of the shield 33 is spaced from thebase to prevent grounding of the shield except through the high radiofrequency impedance to be described.

The trailing edge 35-435 is not joined but is kept open in order toreduce the eddy-currents generated in the conductor 33. The conductor 33is preferably of copper or aluminum material. The conductor 33. isconnected to ground potential through a radio frequency choke 31 byconnection leads 38. The rod ,orantenna wire 321s connected to theprimary 40 of 'the antenna stage coupling transformer 4| by connectionlead 32. The secondary 43 of the antenna transformer-4| is tuned by avariable condenser 44, the output. of which is connected to the radiofrequency amplifier The reception by the vertical rod 32 is similar tothat of any corresponding non-directional mast antenna for use at theradio receiver d5f'or communication or directional reception. I

The high velocity atmospheric particles impinging on the antenna wire 33dissipate their electrical charges therein which electrical charges areconductedto ground through the ra-- dio frequency choke coil 31. Oncethe electrical charges are dissipated in the shield 33 and conducted toground, the shield performs the neutralizing action on the electricallycharged particles. The radio frequency signals pass through the shield33 to the antenna rod 32 losing only a small amount of its energy due tothe high radio frequency impedance of the shield 33 with respect toground potential. The trailing edges 35 of the shield 33 minimizes anycurrent losses induced in the shield by the radio frequency signal wavesto increase the resultant shielding efficiency and increase thesignal-to-static reception ratio by the antenna system. I prefer to makethe radio frequency inductance of the primary 40 of the antennatransformer 41 of lower impedance value than the corresponding radiofrequency impedance of the radio frequency choke coil' 31 connected tothe shield 33. By maintaining such relative impedance ratio, namelymaintaining the shield at a higher impedance with respect to the antenna32, the degree of signal absorption by the shield 33 is furtherdiminished.

To further increase the efliciency of the shield by minimizingeddy-current losses therein, the shield is slotted transversely withslots 46 as shown in Figure 3. Reduction of the eddy-current losses isaccomplished by reducing the mean free electrical path in which any ofthe eddycurrents can now. and is performed by slotting the shield atdifferent portions thereof. The slots 46 divide the shield into acorresponding plurality of segments 41. The segments 41 are electricallyinterconnected and the, connections shown at 48 serve this function.

To assist in the gripping action of the segments 41 of the shield uponthe molded insulation core 36, I. prefer to crimp the slotted edges atregions 46 inwardly to form the crimped edges 43 for the shield segments41. Figure 4 is an enlarged cross-sectional view taken along 4-4 ofFigure 3 illustrating the preferred arrangement whereby the crimpededges 48 at'the slotted portions are set into the molded insulationmaterial 36 and rigidly maintain the shielded structure in place.

In Figure 111 I illustrate a modification of the simpler antistaticnon-directional antenna repreand to the left. The output of the radioreceiver sented in Figure 1. This system comprises two opposed antennamasts 20 and 2| forming a nondirectional antenna. When the masts 26 and.2|

are opposed and are of equal length they form a doublet antenna as iswell known. This modification is independent of the relative lengths orpositions of the masts 26 and 2|. Each of the masts 26 and 2| areenclosed by a metallic shield 22 and 23 respectively. Shields 22 and 23are similar to the hereinabove described shield structure 33 enclosingantenna 32 of Figure 1. The

anti-static shield-s 22 and 23 are conductively connected to ground bytheir respective radio frequency choke coils 24 and 25.

The masts 26 and 2| are connected to the coupling coil winding 26. Thecenter tap 21 of winding 26 is connected to ground potential. Antennae26 and 2| form an efiective non-directional doublet the electricalneutral point 21 of which is connected to ground potential. The winding26 may be replaced by a transmission line to the radio frequencyamplifier 28 at a remote point. A tuned circuit 29 is shown coupled tothe Winding 26 for selectively impressing radio signals induced in theantennae 262 on the radio frequency amplifier 26.

The non-directional antenna systems of Figures 1 and 1A may be employedfor ordinary radio communication upon an aircraft or may be used as thenon-directional antenna of a direction finding system. The metallicshields 22 and 23 conduct the changes of static electricity built up bythe speed of the aircraft through rain, fog, dust and the like toground. The electrical impulses are neutralized with respect to theantenna array 26'2| since the nodal or neutral point of the antenna isconnected to ground. It is to be understood that the antenna array 262|is mechanically supported upon the aircraft. The antenna array 26-2| maybe supported in a vertical position or any other position with respectto the aircraft such as a horizontal position. The system of Figure 1Ais adapted to eliminate any static pulses to an even greater degree thanthe single mast modification of Figure 1.

Figure is a schematic illustration of a rightleft indicating radiodirection finding system of one modification of my present system. Thissystem utilizes a cardioid reception pattern produced by two spaced mastantennae 56 and 5| The masts 56 and 5| are anti-statically shielded bythe conductive shields 52 and 53 individually closing the antennae andconnected to ground through the radio frequency choke coils 54 and 55 ina manner similar to the shielded antenna hereinabove described inconnection with Figures 1 to 4. The size and spacing of the'antennae 56and 5| depend upon the type of vehicle or station it is installed uponand the frequency range it is operated upon. The antennae 56 and 5| areconducted by leads 56 and 51 to an intermediate position where thesignals are combined in accordance with my present invention to producethe right and left cardioid reception patterns. A time-delaynetwork 58is connected in series between either antennae 56 or 5| and the primary66 of th radio frequency coupling coil 6|, the

is correspondingly successively switched to the right and left sectionsof a differentially connected indicating meter 68 by switch 69 operatingin synchronism with the switching system 64 to 61. The theory of theoperation of my present invention may be better understood by thefollowing description in connection with Figures 6 to 23:

In Figure 6 I illustrate the central summation -of signals from twospaced vertical antennae 56 and 5|. The antenna coupling transformer 6|is connected at the mid-position of connection leads 56 and 51. Theprimary 66 of the transformer 6| has its mid-point connected to ground.The secondary 62 of the transformer 6| is connected to the input of theradio receiver 63. Figure 7 illustrates the polar reception pattern ofthe centrally summated spaced antenna system 565|. The polar ordinate atthe angle 9 indicates the relative intensity of the output of theantenna array of Figure 6 in correspondence with the angle of incidence9 of the radio signals as indicated in Figure 6. A centrally summatedspaced mast system produces a figure-of-eight reception pattern havingits null position perpendicular to the plane of the masts.

Figure 8 illustrates the summation of the signals from masts 56 and 5|at the base of one of the antennae. The reception pattern with summationat the left antenna is shown inFiE- secondary 62 of which is connectedto thei p ure 9 as a cardioid with its null position pointing toward theright and'lying in the plane of the masts.

Figure 10 illustrates the summation of the two mast signals at the baseof the right antenna 5| producing the cardioid reception patternillustrated in Figure 11 having its null position pointing toward theleft in the plane of the masts 56 and 5|. The reason for the nullreception pattern produced by the antenna array of Figure 10, forexample, is that the time-phase lag between the signals induced in thevertical mast 56 reaches the primary 66 of the antenna transformer 6| inexact time-phase with the incidence of the signals upon the mast 5|.Since the signals from the antennae 56 and 5| are introduced apart atthe primary winding 66, the eflects of signals in the plane of theantennae 565| coming from the left are nullified to produce the nullshown in Figure 11. Signals originating from the right are impressedupon antenna 5| first and the time-phase displacement between thesignals impressed upon the antenna 56 is twice that corresponding to thespacing between the antennae 56 and 5| since it takes approximatelyequal time intervals for the radiant energy to traverse the spacebetween the antenna 56 and 5| as it takes for the electrical signals totravel across the conductor 56 between the second impressed antenna 56and the primary wind-Y ing 66.

In Figures 12 and 14 are illustrated an antenna system and circuitshaving the antenna transformer 6| located centrally between the. masts56 and 5| and employing a time-delay network 58 to produce a resultantcardioid reception pattern. By placing the time-delay network 58 in theconnection lead 51 from the right hand antenna 5|, the cardioidreception pattern illustrated in Figure 13 is produced with its nullposition toward theright corresponding to Figures 8 and 9. By placingthe time-delay network in circuit with the lead 56 from the left antenna50, the left hand cardioid pattern of Figure 15 is produced. Thetime-delay network 58 is designed to superimpose a time-phasedisplacement upon the antenna. signal conducted to the primary 6B of thetransformer equivalent to the distance between the spaced antenna 50 and5|, namely the time consumed by the travel of the radiant energy betweenthe two masts. With such a time-delay, the signals impressedfrom bothends upon the primary 58 will be substantially equal and of Oppositephase to produce the null as indicated by the illustrated-receptionpatterns.

In Figure 16 I have illustrated the double mast right-left indicatingdirection finding system employing the alternately switched time-delaynetwork 58 with switching circuits 54 to 51 corresponding to the systemof Figure 5. In place of the simple vertical masts 50 and 5| I hereinemploy doublet antenna systems 58' and 5| coupled to the connectionieads55 and 51. through coupling transformers I8 and H. The dipole antennaesystems 50' and 5| are individually nondirectional in character and areparticularly useful for ultra-high frequency reception. By combiningthem with the time-delay network to 'produce the alternate cardioidreception patterns in a manner to be described, an eflicient highfrequency right-left indicating direction finder system is feasible.

Although the dipole antenna structures 58 and 5| may be mounted upon avehicle in a stationary position, they may be rotatably mounted thereonin a manner described in connection with my co-pending applicationSerial No. 139,142, filed April 2'7, 1937, as particularly illustratedtherein in Figure 4. Thus the null position of such direction finder isadjustable by the operator.

The switches 54, 55, 55 and 51 are alternately switched between theircontacts from the solid position illustrated to the opposite position.The alternate switching of these switches connects the time-delaynetwork 58 alternately in series between the antenna connection leads 55and 51 and the primary 50 of the transformer 5|. The illustratedconnections of the switches 54 to 51 connect the time-delay network 58into the connection lead 55 corresponding to the left antenna system 58to produce the left cardioid reception pattern 12 of Figure 17. Curve 12corresponds to the cardioid produced by the system of Figure 14.

The alternate position of the switches 54 to 51 connects the time-delaynetwork 58 into the connection lead .51 producing the right cardioidreception pattern 13 shown in dotted lines in Figure 17 corresponding tothat produced by the system of Figure 12. Continuous alternate switchingof the time-delay network into the left and right antenna connectionscorrespondingly successively produces the left and right cardioid polarreception patterns 12 and I3.

The successive right and left cardioid reception patterns introduce asignal upon the input of radio receiver 63 of magnitude corresponding tothe angle incidence o of the radio waves with respect to the plane ofthe antenna system. a In Figure 17, the angle 9 was shown to interceptthe right and left cardloids to produce different relative magnitudes ofinput for a predetermined signal. As shown in Figure 5, the output ofthe radio receiver is correspondingly switched to the right and leftsections of the differentially indicating meter 58 where the effects ofthe two types of polar reception patterns are algebraically summated toproduce a resultant indication of the needle to the right or left inaccordance with the respective intensities of the reception patterns.

In carrying out my pesent invention, I generate cardioid receptionpatterns solely dependent upon the geometric position of the antennaarray used. By using the time-delay network 58 which is substantiallyindependent of the signal frequencies used, a definite time-lag or phasedisplacement is introduced upon all signals passing therethrough. Thephase, displacement is made to correspond to the actual spacing of theantennae so that all resultant signals introduced to the radio receiver53 will have a cardioid polar receptionpattern.

In Figures 18 to 22, I have illustrated different forms for thetime-delay network 58. In Figure 18, a distributed inductance 14 and 15interconnected by a series of capacitances 15 produces an electricallong line or time-delay network between the input terminals 11 andoutput terminals 18. The characteristic impedance Z0 of such network ispreferably designed equal to the impedance of the individual antennaeand the coupling transformers in order to eliminate interference andreflections as well known in the electrical art. The time-delay networkis designed along well known theory to be substantially distortionlessand independent of frequency discrimination. At the high frequenciesused, the attenuation constant isreadily made substantially negligible.The velocity propagation of the radio frequency currents through thenetwork determines the time-phase displacement between the input andoutput terminals '|'||8. Figure 19 illustrates an alternative longline'or time-delay network composed of one inductance section 88 andaseries of capacitances 8|. Such a halfsection line is preferably usedwhere one side is connected to ground as illustrated.

Figures 20 and 21 illustrate time-delay networks composed of lumpedinductive and capacitive elements 82 and 83 forming balanced andhalf-section time-delay networks corresponding to Figures 18 and 19respectively. By using proper design constants for the respectiveinductances 82 and capacitances 83, a distortionless long linesubstantially independent of frequency and actuation characteristics canbe designed for the frequency bands used for directional reception.

Figure 22 is a continuous long line formed of a conductor 84 centrallypositioned within a shielded housing 85. The distributed capacitance,inductance, resistance and conductance of the transmission line 84--85are proportioned to have the distortionless properties to form thetimedelay network 58. By designing the long line 8485 into a flexibleconstruction, it may be arranged into a form requiring a minimum ofspace.

Figure 23 illustrates the time-delay network corresponding to Figure 21and having lumped inductance'elements 82 and capacitance 83 connected incircuit as the time-delay-network 58 of my right-left indicator systemcorresponding to Figures 5 and 16. The terminals 85--8l are patterns asdescribed in' connection with Figure 17.

The time-delay network may be avoided where further antenna systems arenot objectionable with respect to wind resistance, space, costand thelike. When it is realized that a mast antenna even when streamlinedoffers a minimum aeronetwork hereinabove described is useful forproducing a direction finder system with a minimum number of antennaemasts. In Figure 24 is illustrated a right-left direction finder systemusing cardioid reception patterns produced by four vertical antennaarrays 90 and-9|, 92 and 93 and without using time-delay networks. Theleft antenna system 90-9I is summated by primary winding 94 at the baseof antenna 9|, corresponding to the system described in connection withFigure 10 and produces a left hand cardioid reception patterncorresponding to Figure 11. The right antenna array 92-93 is summated byprimary winding 95 at the base of antenna 92 corresponding to the systemdescribed in connection with Figure 8 and producing a right handcardioid reception pattern corresponding to Figure 9. The

. secondary windings 96 and 91 of the two antenna arrays aresuccessively introduced to the input of radio receiver 63 by the switch98. The output of receiver 63 is alternately introduced to the right andleft sections of the differential indicating meter 68 by switch 69 inthe manner described in connection with Figure 5.

The cardioids produced by the antenna arrays 909I and 92-93 do notdepend on a time-delay network, correspondingly simplifying theswitching system and circuits for producing the alternate right and leftcardioid reception patterns. The reception'patterns depend solely on thegeometric arrangement of the antenna array and the angular position ofthe station and accordingly are not affected by the tuning or tem-'perature. variations or electrical parameter changes of the system. Byrectifying the output of the radio receiver 63 to the extent ofproducing uni-directional current a sensitive direct cur-J rentdifferential meter 68 may be used to summate the effects of thealternate antenna signal outputs to produce the corresponding right orleft.

lar to the plane of the antenna array corresponding to the arrow shownin Figure 17, the position where signals to the right or left will causedeflections of the indicator 68 by signals from that direction producingbalanced or null indications. Although I have illustrated mechanicalswitching arrangement to simplify the theoretical discussion anddisclosures of my present invention I prefer to employ electronicswitching arrangements whereby the transients in the radio frequencynetworks and circuits are eliminated. Such electronic switch systems arewell known in the art and are hereinafter described in connection withthe double and triple mast system but may be equally well employed withthe four mast system of Figure 24.

In Figure 25 is illustrated a vertical mast, cardioid reception pattern.right left indicating direction finder system employing the principlesof my present invention and utilizing three vertical masts to producethe cardioids without timenately produce the right and left cardioidpatterns of Figure 17. The central mast IN is used in place of the twocentral masts 9| and 92 of Figure 24 and is alternately switched to theprimary windings 94 and 95 connecting the left and right antenna mastsI00 and I02 by switch I03. The secondary windings 96 and 91 arecorrespondingly connected to the input of radio receiver 63 bysynchronous operation of the switch 98.

Figure 26 is a schematic diagram of a rightleft'indicator system similarto that of Figure 25. Three vertical masts I00, IOI and I02 are combinedby means of eletronic switching in a manner similar to the mechanicalswitching example of Figure 25. Two diode rectifiers I05 and I06 areemployed with circuit connections for electronically combining thesignals of the antenna masts to successively form right and left cardi-,oid reception patterns at the input of radio receiver 63. The electronicswitching frequency is preferably an audio frequency of the order of onehundred and forty cycles per second. The output of the radio receiver iselectronically switched in synchronism with the antenna system by meansof a third diode rectifier I01.

An audio frequency oscillator I08 comprising the triode I09 generates acurrent of frequency of the order of one hundred forty cycles. An ironcore transformer IIll contains coils III and I I2 coupled to the gridand plate respectively of the triode I09. Secondary windings H3, H4 andH5 are wound on the transformer IIO to transmit the audio frequencygenerated at the transformer to the electronic rectifier tubes I05, I06and I01, The elements a of the rectifier tubes I05 and I06 are connectedto the terminal III; of the winding II3 through individual radiofrequency choke coils III and H8. The I) ends of the rectifiers I05 andI06 are connected to the opposite terminal II9 of the winding H3 toindividual radio frequency choke coils I20 and IN.

The opposite terminals H6 and II9 of the secondary winding 3 are out ofphase with respect to each other and accordingly altemately render the aanodes and the b anodes conductive with respect to the cathodes of therectifiers I05 and I06 in a manner familiar to those skilled in the art.I prefer to connect the caththat the electronic switching circuit isherewith presented schematically and specific biasing conditions of thecathode are omitted for simplicity but are understood by those skilledin the art. The function of the diode rectifiers I05 and- I06 is similarto the operation of the mechanical switches I03 and 98 of Figure 25'where mechanical switching is employed. In this example, however, thealternate conductive nature of the a anodes and the b anodes correspondto the alternate position of the switches 98 and I03 from the solid tothe dotted position.

When the a anodes are conductive with respect to their cathodes, thesignals from masts I00 and IM combine through the primary winding 94 andinduce a cardioid. pattern in the secondary winding 96 which isconducted through the cathode I25 of rectifier I06 to the input of theradio receiver. The D anodes are nonconductive at this period andaccordingly signals from mast I02 and transformer 95-91are ineffective.Conversely, when the b anodes are conductive, the reversed cardioidpattern from masts IOI-I02 combine at transformer 95-91 and actuate theinput of radio receiver 63. The output of the radio receiver receivingthe successive cardioid input voltages is synchronously switched betweenthe left and right sections ofthe difierential indicator 68 through therectifier II. The a anode of rectifier I 01 is connected to the righthand terminal I26 of winding H; the b anode, to the left hand terminalof winding Ill. The terminals I26 and I2! are maintained at similaralternating current voltage potential and 180 out of phase in order torender the a and b anodes of diode I01 alternately 'conductive and insynchronism of the a and b anodes of the antenna diodes I05 and I06. Thealternate conductive nature of the a and b anodes of diode I01 permitsthe rectified cardioid pattern outputs from radio receiver 63 to flowthrough the differential meter 68 in a predetermined manner to producean indication to the right or left in accordance with the position ofthe radio transmitter as will now be evident.

Although I prefer to illustrate the triple mast example with electronicswitching, I do not wish to be limited thereto since the establishedprinciples of electronic switching may be employed.

in the four mast case corresponding to Figure 24 as well as to the twomast case of Figures 5, 16 and 23 employing the time delay network 58.The electronic switching renders the diode anodes successivelyconductive with respect to the common cathode and permits the conductionof the radio frequency currents at the antenna stage to be combined in apredetermined manner similar to the simplified showing with themechanical switching illustrations.

Although I have illustrated preferred forms for carrying out my presentinvention, it is to be understood that modifications are feasible and Ido not intend to be limited except as set forth in the following claims.

I claim:

1. A radio direction finder system comprising a first non-directionalantenna; a second nondirectional antenna; means for combining the signaloutputs of said first and second antennae to successively formdifierently oriented polar cardioid reception patterns; an indicator;and means for producing right-left indications on said indicator inaccordance with the relative position of the antennae with respect tothe signal source.

2. A radio direction finder system comprising a first non-directionalantenna; a second nondirectional antenna; means for combining the signaloutputs of said first and second antennae and means for alternatelydelaying the outputs of said antennae with respect to each other tosuccessively form differently oriented polar cardioid receptionpatterns, comprising a time delay network in. circuit with saidantennae; an indicator; and means for producing right-left indicationson said indicator in accordance with the relative position of theantennae with respect to thesignal source.

3. A radio direction finder system comprising a first non-directionalantenna; a second nondirectional antenna; and means for combining thesignal outputs of said first and second antennae to successively formdifferently oriented polar cardioid reception pattems,.a time delaynetwork and switching means for alternately connecting said network incircuit with said first and second antennae.

4. A radio direction finder system comprising mast antenna; a radioreceiver responsive to said antenna signals; an indicator connected tothe output of said receiver; means for alternately combining the signaloutputs of said first and second antennae to successively formdifferently oriented polar cardioid reception patterns and switchingmeans for alternately connecting a time delay network in circuit withsaid first and second antennae; and means for correspondingly switchingthe output of said receiver at said indicator for producing right andleft deflections in accordance with the direction of the signaltransmitter with respect to the position of said antennae.

5. A radio direction finder system comprising a first vertical mastantenna; a second vertical mast antenna; a radio receiver responsive tosaid antenna signals; a differential indicating meter connected to theoutput of said receiver; and means for alternately combining the signaloutputs of said first and second antennae and means for alternatelydelaying the outputs of said antennae with' respect to each other tosuccessively form right and left oriented polar cardioid receptionpatterns comprising a time delay network.

6. A radio direction fin'der system comprising a first non-directionalantenna; a second nondirectional antenna; a radio receiver responsive tosaid antenna signals; a differential indicating meter connected to theoutput of said receiver; means for combining the signal outputs of saidfirst and second antennae to successively form right and-left orientedpolar cardioid reception patterns comprising a time delay network andswitching means for alternately connecting said network in circuit withsaid first and second antennae; and means for correspondingly switchingthe output of said receiver at said differential meter for producingright and left deflections in accordance with the direction of thesignal transmitter with respect to the position of said antennae.

7. A radio direction finder system comprising a first non-directionalantenna; a second nondirectional antenna; a radio receiver responsive tosaid antenna signals; an indicator. connected to the output of saidreceiver; means for combining the signal outputs of said first andsecond antennae to successively form differently oriented polar cardioidreception patterns comprising a time delay network and switching meansfor alternately connecting said network in circuit with said first andsecond antennae; and means for correspondingly switching the output ofsaid receiver at said indicator for producing right and left deflectionsin accordance with the direction of the signal transmitter with respectto the position of said antennae.

8. In a right-left indicating direction finding system, a plurality ofnon-directional antennae; circuit connections extending from saidantennae for combining the signals from said antennae to producenon-symmetrical polar patterns an indicator connected to said circuitconnections: and means whereby said indicator is alternately controlledby signals forming said patterns to produce right-left indications inaccordance with the relative position of the antennae with respect tothe signal source.

v 9. In a right-left indicating direction finding system, a plurality ofnon-directional antennae in spaced relation: means for combining thesignals intercepted by said antennae to produce alternate reversednon-symmetrical polar patterns; an indicator and means for alternatelyapplying the signals forming each of said patterns to said indicator;and means whereby said indicator operates in response to said signalsfor producing right-left indications in accordance with the relativeposition of the antennae with respect to the signal source.

10. In a right-left indicating direction finding system, a plurality ofnon-directional antennae in spaced relation; means for combining thesignals intercepted by said antennae to produce alternate reversednon-symmetrical polar patterns; an indicator and means for alternatelyapplying the signals forming each of said patterns to said indicator;and means whereby said indicator operates in response to said signalsfor producing right-left indications in accordance with the relativeposition of the antennae with respect to the signal source and inaccordance with the sense of said signals.

11. In a right-left indicating direction finding system; a plurality ofantennae in predetermined spaced relation; a time delay network having atime delay characteristic in accordance with the spatial relation ofsaid antennae; an indicator; circuit connections to said indicator; andswitching means for interposing said time delay network between saidcircuit connections and each of said antennae successively and forsimultaneously connecting the other of said antennae in circuit withsaid circuit connections.

12. In a right-left indicating direction finding system; a plurality ofantennae in predetermined spaced relation; a time delay network having atime delay characteristic in accordance with the spatial relation ofsaid antennae; said network being connected in series with saidantennae; an indicator; circuit connections from said indicator to saidantennae circuit; and switching means for successively switching saidtime delay network between each of said antennae and said circuitconnections.

' 13. In a right-left indicating direction finding system; a pluralityof antennae in predetermined spaced relation; a time delay networkhaving a time delaycharacteristic in accordance with the spatialrelation of said antennae; said network being connected in series withsaid antennae; an indicator; circuit connections from said indicator tosaid antennae circuit; switching means for successively switching saidtime delay network between each of said antennae and said' circuitconnections; and switching means for correspondingly successivelyreversing said indicator with respect to said circuit connections.

14. In a right-left indicating direction finding system; a plurality ofantennae in predetermined spaced relation; 2 time delay network having atime delay characteristic in accordance with the spatial relation ofsaid antennae; said network being connected in series with saidantennae; a translating means connected in said series circuit; andswitching means for switching said time delay network between each ofsaid antennae and said translating means successively for producing .aplurality of non-symmetrical polar patterns.

15. In a right-left indicating direction finding system; a plurality ofantennae in predetermined spaced relation; a time delay network having atime delay characteristic in accordance with the spa ial relation ofsaid antennae; said network being connected in series with saidantennae; a translating means connected in said series circuit;switching means for switching said time delay network between each ofsaid antennae and said translating means successively for producing aplurality of non-symmetrical polar patterns; an indicator; circuitconnections from said indicator to said translating means; and meanswhereby said indicator operates to indicate the relative position of theantennae with respect to the signal source.

16. In a right-left indicating direction finding system; a plurality ofnon-directional antennae in spaced relation; an indicator; means forproducing cardioid patterns by means of said antennae in accordance withthe orientation thereof switching means for reversing said patterns;means for alternately impressing said signals on said indicator toindicate to the right or left of the direction of the incident signal,depending upon the angular position of the plane of the antennae withrespect to the signal source.

EDWARD J. HEFELE.

